Air Quality Guidelines - World Health Organization Regional Office ...

inorganic pollutants
167
In early studies on platinum-exposed workers, exposure levels were high.
Values ranged from 0.9 to 1700 µg/m 3 in four British platinum refineries,
giving rise to symptoms in 57% of the exposed workers (6). Following the
adoption of an occupational exposure limit with a threshold limit value
(TLV) for soluble platinum salts of 2 µg/m 3 as an 8-hour time-weighted
average, the incidence of platinum salt hypersensitivity has fallen, but
sensitization in workers has still been observed. Thus, in a cross-sectional
survey, skin sensitization was reported in 19% of 65 workers in a platinum
refinery, where analysis of airborne dust showed levels of soluble platinum
of 0.08–0.1 µg/m 3 in one department and less than 0.05 µg/m 3 in other
areas (7). In another plant with air levels generally below 0.08 µg/m 3 , 20%
of exposed workers were sensitized (8). It is possible, however, that short,
sharp exposures to concentrations above the TLV could have been responsible
for some of these effects. In a 4-month study in a United States platinum
refinery with a high prevalence of rhinitis and asthma, workplace
concentrations exceeded the occupational limit of 2 µg/m 3 for 50–75% of
the time (9). The risk of developing platinum salt sensitivity appears to be
correlated with exposure intensity, the highest incidence occurring in groups
with the highest exposure, although no unequivocal concentration–effect
relationship can be deduced from the reported studies.
Health risk evaluation
There is no convincing evidence for sensitization or for other adverse health
effects following exposure to metallic platinum. Exposure to the halogenated
platinum complexes already described has given rise to sensitization
following occupational exposure to platinum concentrations in air greater
than the TLV of 2 µg/m 3 , and may have caused sensitization reactions at
concentrations down to and even below the limit of detection in workplace
monitoring of 0.05 µg/m 3 . Furthermore, as subsequent exposure to minute
concentrations of these platinum salts may lead to a recurrence of the health
effects shown in Table 20 in previously sensitized subjects, it is not possible
to define a no-effect level for these platinum compounds.
Because the correlation between platinum exposure concentration and the
development of sensitization is unknown, the WHO Task Group (2) considered
that a recommendation for a reduction in the occupational exposure
limit cannot at present be justified. It did, however, recommend that
the occupational exposure limit of 2 µg/m 3 be changed from an 8-hour
time-weighted average to a ceiling value, and that personal sampling devices
be used in conjunction with area sampling to determine more correctly the
true platinum exposure. Should it be ascertained unequivocally that
sensitization has occurred in workers consistently exposed to platinum